La Fosse Dionne

In the heart of Tonnerre, the Fosse Dionne is a Vaucluse spring with a varied but perpetual flow. It was converted into a washhouse in 1758 by the father of the Chevalier d'Éon. The Fosse Dionne has always intrigued and the first explorations date back to the 19th century. Nevertheless, it has kept its secret: the origin of the spring. The result of a complex course of exsurgences and resurgences, this spring forms a basin at the bottom of which we can see the start of a gallery. The known route leads 360 m from the mouth and to a depth of 61 m. The Fosse Dionne is so intriguing and mysterious that it has given rise to many legends: the basilisk snake, the devil's coins and many others...